Saturday, October 8, 2011

In the late nineteenth century, much of the United States was a frontier where people sought to realize their American dream, and many of them headed to the vast prairies of this continent. The term prairie conjures up images of beautiful, undulating plains stretching as far as the eye can see, yet this image is not altogether accurate. In the winter, these plains get bitterly cold, and in the summer, they are blistering hot. Add to this an almost perpetual wind, and what you get is an unforgiving environment. As if these tough conditions weren’t enough for the settlers, they were also confronted with an insect that amassed in swarms of a gargantuan nature.

The Rocky Mountain locust was small by typical locust standards, with an adult body length of 20 to 35 mm, long wings that extended past the end of the abdomen, and the enlarged back legs common to most grasshoppers. What this insect lacked in individual size it more than made up for in the size of its aggregations. Locusts, for much of the time, live their lives in the same way as most other grasshoppers—going about their business without being much of a nuisance to anyone—but occasionally, their populations may become very dense, and this triggers a dramatic change. The locusts change color, their wings grow, and they start to amass in swarms.

The swarms formed by the Rocky Mountain locust were incredible and probably represent some of the biggest aggregations of any land animal that has ever existed. A swarm observed in Nebraska during the summer of 1874 was of staggering proportions. Dr. A. L. Child of the U.S. Signal Corps was charged with assessing just how big this swarm was, and to get an idea, he measured the speed of the locusts as they were fl ying past and then telegraphed surrounding towns to get an idea of its extent. The swarm was estimated to be about 2,900 km long and 180 km wide. Observers in the Nebraskan towns over which this swarm passed reported that the gigantic cloud of insects obscured the sun and took five days to pass overhead. This begs the question of how many locusts there were in this enormous swarm. Estimates are as close as we’ll ever get, but it has been calculated that there must have been around 12 trillion insects in this aggregation. All these fl uttering insects weighed somewhere in the region of 27 million tonnes, and if the desert locust of the Old World is anything to go by, then this swarm may have eaten its own weight in food every day just to sustain itself. Luckily, the Rocky Mountain locust was not a fussy eater—it would nibble a huge range of plants, and in the absence of foliage, it would munch bark, leather, laundry, dead animals, and even the wool off a sheep’s back. As can be imagined, the multitude of mandibles left a trail of devastation, and between 1873 and 1877, the vast swarms of insects caused massive crop damage in Nebraska, Colorado, and some other states, estimated at around $200 million.

Around 30 years after these immense swarms left a trail of devastation in their wake, the Rocky Mountain locust mysteriously vanished. The reason behind the extinction of this insect has been speculated on for some time. Some experts have suggested that the species never became extinct and that the locust was actually the swarming phase of a species that can still be found today, a theory that has been shown to be incorrect. The likely explanation for the disappearance of this insect is that outside of its swarming periods, the locust retreated to the sheltered valleys of Wyoming and Montana, where the females laid their eggs in the fertile soil. These very same valleys attracted the attention of settlers, who saw their potential for agricultural endeavors, and with their horses and their plows, they turned the soil over and grazed their livestock on the nutritious grass. These actions destroyed the eggs and developing young of the insect, and around three decades after its swarms blotted out the sun, the Rocky Mountain locust was gone forever.